The inventive concept relates to a nanorod light emitting device capable of reducing a leakage current, and a method of manufacturing the same.
Light emitting devices may emit light by combination of electrons and holes injected into an active layer via a p-n junction structure of a semiconductor. Semiconductor light emitting devices may be classified into light emitting diodes (LEDs) and laser diodes (LDs). LEDs are regarded as highly efficient and environment friendly light sources due to their high brightness and relatively low power consumption, and thus, may be used in, for example, displays, optical communications, motor vehicles, and general lighting devices. Semiconductor light emitting devices use electroluminescence, i.e., a phenomenon whereby light is emitted from a semiconductor layer due to application of a current or a voltage. When electrons and holes are combined in an active layer of a semiconductor light emitting device, energy corresponding to an energy bandgap of the active layer may be emitted in the form of light. Accordingly, the wavelength of light emitted from the semiconductor light emitting device may vary according to the size of the energy bandgap of the active layer. Recently, blue LEDs and ultraviolet LEDs using nitride having excellent physical and chemical characteristics have been introduced. Also, since white light or other monochromatic light may be formed by using a blue or ultraviolet LED and a fluorescent material, the application range of light emitting devices has broadened. However, since a plurality of crystal defects generally exist in nitride-based compound semiconductor crystals, if electrons and holes are combined in crystals having defects, heat energy may be emitted instead of light energy and thus a luminous efficiency may be reduced.
Crystal defects may occur due to a mismatch in lattice constants or a difference in thermal expansion coefficients between a substrate and a compound semiconductor. In order to reduce crystal defects, a light emitting structure having a nanorod shape has been developed. Such structure has a smaller area contacting a substrate in comparison to a structure having a thin film shape, and thus, a mismatch in lattice constants or a difference in thermal expansion coefficients may occur less in comparison to the structure having a thin film shape. Currently, a core/shell nanorod structure has been suggested. One of the advantages of the core/shell nanorod structure is that crystal defects may be minimized. General light emitting devices having a thin film structure mainly have two types of crystal defects. The first crystal defect is mismatch dislocation caused by a lattice mismatch between a quantum well layer formed of InGaN and a quantum barrier layer formed of GaN. In this case, the mismatch dislocation exists in parallel in a growth layer. The second crystal defect is threading dislocation occurring on an interface between sapphire and GaN and reaching an emission layer in a direction in which a light emitting device structure grows.
In a nanorod structure, since a GaN layer may also grow in a horizontal direction, lattice mismatch dislocation may be reduced in comparison to general light emitting devices having a thin film structure. Also, since an area of a nanorod structure on a substrate is small, only a part of threading dislocation propagates to an active layer, and even when dislocation occurs, the dislocation may probably move to a near surface and may disappear. Second, since an active layer is formed along surfaces of cores in the form of a shell layer, an area of a light emitting surface may be increased, a current density may be reduced, and thus, a luminous efficiency may be improved.